In a typical diesel fuel supply circuit, a reservoir or tank is provided with diesel fuel that in turn is supplied to the diesel engine. A recirculating diesel fuel circuit is connected between the engine and the fuel tank in which one fuel line extends from the fuel tank to the diesel engine to supply the engine with fuel, and another fuel line extends from the diesel engine back to the fuel tank to return overflow fuel to the tank.
At least one pump is provided in this closed loop circuit to pressurize the diesel fuel and move it from the fuel tank through the engine and back to the tank.
An excess of diesel fuel is usually provided by the pump, such that when the operator places a large demand on the engine, for example by stepping on the accelerator pedal, there will be sufficient diesel fuel supply to the engine to meet any power demand. When the operator does not need as much power, he releases the accelerator pedal, permitting the engine to slow to idle or to some lower power setting in which the engine consumes much less fuel.
The pump, producing an excess of fuel, must be allowed to send the excess fuel somewhere. For this reason, a bypass valve is provided in the fuel circuit that lets this excess fuel from the pump bypass the engine and go back to the fuel tank.
The process of pressurizing the fuel and routing it through the engine compartment causes the diesel fuel to heat substantially. The temperature may be as high as 100 or 110° C. This heat must be removed before the fuel was returned to the fuel tank. For this reason, a fuel cooler is typically provided in the return path of the fuel from the engine to the fuel tank.
In a new arrangement, however, vehicles have been provided with fuel tanks that are made of a conductive material, such as a light metal alloy, and are disposed in or adjacent to the engine compartment itself where the heat is generated. This has resulted in the fuel tank absorbing a significant amount of heat from the environment.
This additional heat transmitted to the fuel in the fuel tank poses a problem. Fuel that starts from the fuel tank at an elevated temperature (e.g. 70° C.) can damage other engine components.
It is an object of this invention to provide a diesel fuel supply circuit that reduces the temperature of the fuel provided to the engine. This benefit is provided by the invention as recited in claim one. Additional improvements are provided by the modifications described in the other claims.